The teenage girls chatted to each other and their teachers as the school bus rattled along the country road. Students from a girls’ high school in Swat, they had just finished a term paper, and their joy was evident as they broke into another Pashto song. About a mile outside the city of Mingora, two men flagged down and boarded the bus, one of them pulling out a gun. “Which one of you is Malala Yousafzai?” he demanded. No one spoke—some out of loyalty, others out of fear. But, unconsciously, their eyes turned to Malala. “That’s the one,” the gunman said, looking the 15-year-old girl in the face and pulling the trigger twice, shooting her in the head and neck. He fired twice more, wounding two other girls, and then both men...